In optical communications networks, optical transmitter modules, optical receiver modules, and optical transceiver modules are used to transmit and receive optical signals over optical fibers. In a transmit portion of such an optical module, a laser generates modulated optical signals that represent data, which are then transmitted over an optical fiber. The laser can be, for example, a Vertical Cavity Surface Emitting Laser (VCSEL) or an edge-emitting laser. In a receive portion of such a module, an optics system directs light propagating out of the end of an optical fiber onto an optical detector or photodetector, which converts the optical energy into electrical energy. A photodetector is typically a semiconductor photodiode device, such as a PIN (p-type/intrinsic/n-type) photodiode. Optical transceiver modules typically include multiple lasers for transmitting multiple data signals and multiple photodiodes for receiving multiple data signals.
An optical module is commonly assembled by mounting the optoelectronic device, i.e., laser or optical detector, on a substrate, also referred to as a leadframe. As the optoelectronic device typically comprises a microelectronic semiconductor die, electrical connections between the die and conductors on the substrate are made by a technique known as wirebonding. Wirebonding is a technique in which one end of a very fine wire, known as a bond wire, is bonded to a bond pad on the die using thermal or ultrasonic energy, and the other end is bonded to a bond pad on the substrate. A lens assembly can be aligned with the transmit or receive optical ports of the die and mounted in fixed relation to the die and substrate.
Bond wires are extremely fragile because the wires are extremely fine, i.e., very thin gauge. Rough handling of the optical assembly can easily break or dislodge a bond wire. In some optical assemblies, the bond wires are protected by an enclosure or module body that encloses the entire optical assembly. In some assemblies, the bond wires are encapsulated in a dielectric resin to protect them from external forces that can break or dislodge them.
While the aforementioned techniques may be effective at protecting the bond wires from external forces that can break or dislodge them, they are not aimed at, and are not effective at, protecting the bond wires and/or the bond pads from electro-chemical reactions/ion migration that can degrade the integrity of the bond wires and/or of the bond pads. A need exists for such a solution.